Question for Reverse Flow Owners

[Brew-Bq]

We bought a custom built trailer mount reverse flow pit used, and after a few cooks I have a couple questions. First off its a propane tank style "loosely" based off a Shirley design. 56"Lx24"W- one big lower rack and a smaller upper pull out. 24"x24" firebox w a Warmer w 3 racks directly above said Firebox of the same dimensions. Original owner said it was originally designed to flow smoke through the cook chamber and wamer/cook chamber but they added an adjustable baffle between the warmer and main chamber and a new stack to the main chamber. The original stack in the warmer is 4" and the new one in the main chamber is 6" both with adjustable dampers so you can close off the warmer if you like. The RF plate runs the length of the chamber with maybe 3 or 4" opening at the tongue end. Right above the RF opening is a angled heat deflector w a 1" gap to allow heat to go up to the top shelf while directing some to the bottom. In trying to even out the temps a bit im wondering how yours is set up? Is there a deflector at the end of the RF plate? I get a real hot spot on the top and bottom of the tongue end. If I put a split right at the end of each grate to block heat the bottom stabilizes and the top still runs 50-70F hotter. Upper rack on stack end is coolest spot and bottom firebox is hot but not as hot as the other end. I have run w the warmer shut down (175-200F) and the main chamber (6")stack wide open. I get a real nice clean burn but it tends to run pretty hot which Im fine with say 350F in the hottest spot and 250 in the coolest. One thing Im wondering is if the stack is oversized and I should choke it a bit. The previous owner ran it more than 1/2 way closed. I had a bit of trouble keeping the draft going good but that was a windy day and our first cook. I know this post is all over the place but any ideas about how to even it out a bit more? Design flaws? I do love cooking on it even with all the variation and I realize 3 cooks is not a lot of testing. Ran 4 mavericks on each end top and bottom. Two mounted Tel Trues have the probes set right where bottom of the top rack starts and give a real rough idea of temps. And I did experiment w raising and lowering the tongue w little change.

 

[BBQ Freak]

can you take a pic of the angled piece ? that is confusing me .

 

[AZRaptor]

I checked my Shirley and there is no deflector over the opening from the RF plate, it's a clear shot to the top of the cook chamber. I also checked and both of my stacks are 6" and I run whichever one I'm using wide open so I don't think the new 6" one is too big.

 

[pjtexas1]

I think on the regular cabinet model the round tank might act as a deflector. Unless I'm not understanding the question about the opening.

 

[Brew-Bq]

This is a crappy pic but its all I got. Think the heat deflector on an old OK Joe right after the firebox but with a gap. In the pic you can see the end of RF plate at the bottom and the angled deflector tacked on above w a couple tabs. I can only guess they were trying to direct some of the heat to the main grate. Theres about a 1" gap where it meets the rounded end of the chamber where heat can flow straight up. It would be very easy to remove.

 

[Brew-Bq]

Should have posted this earlier but here is the cooker.

 

[dtyates]

Hard to say without knowing your dimensions, but I'd say your opening at RF plate to chamber isn't big enough and that baffle plate probably isn't necessary. Your going to run hotter on the top rack, as you know, heat rises. I would try plugging your numbers into feldon calculator. Also, using feldon for a reverse flow, I've heard to multiply final numbers by 1.5 to get openings correct. Don't know if anyone else has heard this. Something that I do to help even Temps some is place a water pan on the RF plate over the hot spots.

 

[Doug Crann]

Might want to use this calculator...
http://www.smokingmeatforums.com/t/...daveomak-and-others-ready-to-use-rev5-6-19-15

 

[Brew-Bq]

Might want to use this calculator...
http://www.smokingmeatforums.com/t/1...e-rev5-6-19-15

Thanks for the link! That looks pretty comprehensive. Ill try to find time tomorrow to get over to the warehouse and measure everything. I will say the thing draws and comes up to temp like a champ so it doesnt seem restricted. But maybe a small change will help out. I need more practice to.

 

[Bob O Q Shawtee]

You might try removing the baffle then build 2 or 3 plates that can be moved/repositioned around the chamber. An oversize passage from fire box to chamber alow's me to regulate draft at that point according to type wood and moisture. A wide open stack normally works best for me.

 

[ButtBurner]

Hard to say without knowing your dimensions, but I'd say your opening at RF plate to chamber isn't big enough and that baffle plate probably isn't necessary. Your going to run hotter on the top rack, as you know, heat rises. I would try plugging your numbers into feldon calculator. Also, using feldon for a reverse flow, I've heard to multiply final numbers by 1.5 to get openings correct. Don't know if anyone else has heard this. Something that I do to help even Temps some is place a water pan on the RF plate over the hot spots.

I would agree with this is if I am reading this right

the gap between the far end of my rf plate and the cook chamber wall is at least 6" if yours is one 1" I would look at that for the problem

 

[dtyates]

The openings at the firebox and the end of RF plate are ideally supposed to be close to same to allow even air flow throughout. Working off of feldons Calc I had to make the opening at end of RF plate 7 inches to equal fire box opening. My RF smoker moves lots of air and has fairly even temperatures from side to side. The top rack is naturally hotter and the RF plate gets hot at the firebox but a half pan with water fixes that.

 

[Brew-Bq]

To clarify, the RF plate ends 4-6" before the end of the cooker. Its the little deflector above the RF that has a 1" gap on the back of it but thats just to allow heat to go straight to the top and the rest gets pushed towards the bottom grate but it doesnt restrict flow, just directs it. I didnt have time at work to take the measurements today, never got over to the warehouse. Ill probably remove the deflector since no one else seems to use one. Then at least Ill be operating closer to normal for a RF.

 

[BBQ Freak]

so if I see right the bid square box is pretty much cover the whole end ? is so I would remove and see what happens and you can always put it back .

 

[BBQ Freak]

here is a pic of mine that I had , wide open .

 

[AZRaptor]

here is a pic of mine that I had , wide open .

BBQ Freak I saw the pic of your warmer damper in the other thread and this pic here, are these pics from when you first got it or do you really keep it THAT clean? :biggrin1:

 

[BBQ Freak]

BBQ Freak I saw the pic of your warmer damper in the other thread and this pic here, are these pics from when you first got it or do you really keep it THAT clean? :biggrin1:

that was when I was new and never cooked in , lol . I might keep the outside that clean after using but the inside was nice and black with a few chunks .:razz: